C header includes C++ Header

[Matthew-w56]

I am attempting to use the Dart FFIGen to generate a binding for a library written in C++, with C-compatible headers. When I run the FFIGen, I get the following errors:

`PS C:\Users\mbwil\Documents\Programming\Flutter\guido_integration> dart run ffigen -v fine

[INFO] : Running in Directory: 'C:\Users\mbwil\Documents\Programming\Flutter\guido_integration'

[FINE] : Adding header/file: C:\Users\mbwil\Desktop\guidolib\src\engine\include\GUIDOEngine.h

[FINE] : CompilerOpts used: []

[INFO] : Input Headers: [C:\Users\mbwil\Desktop\guidolib\src\engine\include\GUIDOEngine.h]

[FINE] : Creating TranslationUnit for header: C:\Users\mbwil\Desktop\guidolib\src\engine\include\GUIDOEngine.h

[SEVERE] : Header C:\Users\mbwil\Desktop\guidolib\src\engine\include\GUIDOEngine.h: Total errors/warnings: 20.

[SEVERE] : C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.39.33519\include\yvals_core.h:28:2: error: Error in C++ Standard Library usage [User-Defined Issue]

[SEVERE] : C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.39.33519\include\yvals.h:334:1: error: unknown type name 'namespace' [Semantic Issue]

[SEVERE] : C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.39.33519\include\yvals.h:334:1: error: expected ';' after top level declarator [Parse Issue]

[SEVERE] : C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.39.33519\include\cstdlib:22:62: error: expected function body after function declarator [Parse Issue]

[SEVERE] : C:\Program Files (x86)\Windows Kits\10\Include\10.0.22621.0\ucrt\corecrt_wstdio.h:34:14: error: unknown type name 'FILE' [Semantic Issue]`

The second error stands out to me as the reason for the cascade of issues. Specifically, the build tools in the visual studio folder are C++ headers, and use the namespace keyword. This causes the tool to fail because C doesn't support this. So what is there to be done to avoid this collision?

Is there something in the internals that needs to be able to deal with C++ headers being depended on within the build tools, or am I missing a way around this problem?

Extra Information:

• Windows 10
• Library is GuidoLib (sheet music engraving library)

Thanks for any help!

[dcharkes]

Just googling around:

https://github.com/microsoft/STL/blob/main/stl/inc/yvals.h#L334C1-L334C11

_STD_BEGIN // equal to namespace mynamespace {

https://stackoverflow.com/questions/41536696/how-where-c-namespace-std-is-defined-link-to-documentation-standard

C doesn't have namespaces.

So the headers are at least not transitively compatible with C.
Maybe it will succeed if you set a filter on what bindings are generated to not generate for the MSVC and Windows includes.

headers:
  entry-points:
    - ...
  include-directives:
    - 'C:\Users\mbwil\Desktop\guidolib\src\engine\include\**'

[Matthew-w56]

Is there a way to filter like that? This is my configuration and it seems to include what it needs to the in the project without explicitly including those c++ headers.

ffigen:
output: 'lib/guido/generated_bindings.dart'
name: 'GuidoWrapper'
description: 'Guido C Library wrapper for Dart'
ignore-source-errors: true
functions:
expose-typedefs:
include:
- '.*'
headers:
entry-points:
- 'C:/Users/mbwil/Desktop/guidolib/src/engine/include/GUIDOEngine.h'
include-directives:
- 'C:/Users/mbwil/Desktop/guidolib/build/lib/GUIDOEngine64.dll'
- 'C:/Users/mbwil/Desktop/guidolib/build/lib/GUIDOEngine64.exp'
- 'C:/Users/mbwil/Desktop/guidolib/build/lib/GUIDOEngine64.lib'
- 'C:/Users/mbwil/Desktop/guidolib/src/include'
- 'C:/Users/mbwil/Desktop/guidolib/src/engine/include/**'
- 'C:/Users/mbwil/Desktop/guidolib/src/lib'
- 'C:/Users/mbwil/Desktop/guidolib/build'

[dcharkes]

I'm not familiar with the Windows headers here.

I'd expect the _STD_BEGIN macro to be defined as empty for C compatibility.
If the _STD_BEGIN is unconditionally defined as a namespace, it is not C compatible.

Googling some more:
https://github.com/microsoft/STL
This is the C++ standard library. So it's unsurprising it's incompatible with C.
Are you sure what's in your include-directives is C compatible only?
Maybe try removing things from your include-directives to generate less and try to only generate for the single header file?

ignore-source-errors: true

You might want to remove this to triage errors.